----------------------
                                    |--------| web1/apache/centos |--------|        -----------------------
-------------------------------     |        ----------------------        |--------| db01/centos/mariadb |
| ha01/haproxy/acme.sh/centos |-----|                                      |        -----------------------
-------------------------------     |        ----------------------        |--------| cache01/debian/redis|
                                    |--------| web2/nginx/debian  |--------|        -----------------------
                                             ----------------------